Thank you for writing.
I am sorry to hear about this negative experience of yours. The information provided makes me think that there are assembly version mismatch in your project, so may I please ask you to check the versions of all Telerik assemblies referenced in your project and make sure they are precisely
Also, can you please share which version(s) of Telerik UI for WinForms you have installed on your machine?
I am looking forward to your reply.